Ventilating fan



Filed Feb. '7, 1935 Snnentor Patented June 9, 1936 v UNITED STATES PATENT OFFICE VENTILATING FAN Frederick Charavay, Piqua, Ohio, assignor of one-half to Hartzell Industries, Inc., Piqua, Ohio, a corporation of Delaware I Application February 7, 1935, Serial No. 5.32s 7 8Glaims. (01.170459) t This invention relates to ventilating fans-and the like.

One object of the invention is the provision of a ventilating fan having a blade construction such as to provide for efncient operation with a greatly reduced noise generation, especially at high speeds of operation.

, Another object of the invention-is the provision of a rotatable air ventilating propeller having 10 a blade in which the leading edge from the midportion thereof to the blade tip is swept back at a relatively high angle with respect to a radial line from the axis of rotation, and in which the blade sections are of aerofoil shape and are heli cally displaced to provide for outwardly decreasing angles of attack,

Another object of the invention is the provision' of a rotatable air ventilating propeller having any desired number of blades constructed generally in the form of the wing of a bird and arranged to provide for eiiicient movement of the air but with unusual quietness.

Other objects and advantages of the invention will be apparent from the following description, the appended claims and the accompanying drawing, in which- Fig. 1 is a plan view of a ventilating propeller embodying the present invention;

Fig. 2 is an enlarged plan viewof one of the I propeller blades; and

Fig. 3 is a. view of one of the blades looking transversely of the axis of rotation and showing the sectional formation and angular positioning of the sections.

Referring more particularly to the drawing by reference numerals,fl0- designates generally a propeller, of metal, laminated wood, or other suitable material, having a plurality of blades H which extend generally outwardly from the central hub portion l2. The latter is provided preferably with a central opening l3 by means of which thehub of the propeller can be mounted on a suitable operating shaft, it being understood that the ventilating propeller I0 is adapted to be driven at high speed by means of an electric motor or speed, is of a constant pitchit is quite objectionable in a great many locations of use. The present blade construction has; been found in actual practice to cause a great reduction in the amount of sound generated by the ventilator. 5

As will be apparent from Fig. 2 ofthe drawing, in whichthe blade is viewed looking in the direction of the axis of rotation, the leading edge 14 preferably extends outwardly and forwardly from the thick hub portion l5, and then bends 10 angle of the order of about 45 degrees to'thegq radial line I1 although this angle may be considerably less than 45 degrees or may be quite considerably larger. In the case of the propeller herein shown and described for exemplary purposes the propeller is of 32 inch diameter and 5 adapted for operation at a speed of about 1100 R. P. M. However, the invention is not at all limited to this particular speed of operation or the particular propeller'diameter referred to.

It will be noted that the-leading edge of the 30 blade departs greatly from a radial line from the axis of rotation, and the body of air out by the blade is therefore struck at any one instant by the various portions of thefront of the blade throughout a widely distributed area insteadof 5 through a localized more or less radial area, the result being a great reduction in the amount of noise produced. The trailing edge 20 of the blade also departs very materially from astraight radial line from the axis of rotation, and this has also 40 been found to reduce the amount of noise produced. The general-appearance of the blade, as will be apparent from Fig. 2, is that of a bird's wing, the outer portion of the blade being considerably back of the effective mid portions of the 45 blade. This figure also shows how the centers of the chord lengths taken at various distances from the axis of rotation beyond the mid portion of the blade lie in a line which is curved outwardly and backwardly at a large angle, this line being represented by the numeral 2|.

Fig. 3 shows a series of annular sections a, b, c, d ande taken respectively on the lines 3a, 3b, 3c, 3d and 3c of Fig. 2. These blade sections, as will be apparent from Figs. 2 and 3, increase in chord length from the hub outwardly to approximately the mid blade length and then decrease outwardly to the tip, the greatest chord length being at a point preferably somewhat closer to the axis than to the tip, and not outwardly of the mid portion. The blade, in efiect, is helically twisted so that the angles of attack of the various blade sections decreases outwardly from a point near the hub portion to the blade tip. Thus the angle of attack of the particular section a is represented by the angle A while B, C, D and E represent the angles of attack of the blade at the corresponding sections 3b, 3c, 3d and 3e. The angles A to E inclusive,-that is the angles of the blade sections with respect to the plane of rotation, are about 33 degrees, 25 degrees, 18 degrees, 15 degrees and 12 degrees, respectively in the particular propeller herein described in detail, these angles being chosen in accordance with the power, diameter and speed requirements. As will also be apparent from Fig. 3, the approximate centers of gravity 'of the various sections throughout the main inner portion of the blade lie in the plane of rotation butt the centers of gravities of the outer tip portions are deflected upstream as shown by the location of the section e with respect to the plane of rotation shown by the dash line in Fig. 3.

The blade is of high efliciency, inasmuch as the various sections taken at diflerent distances from the axis of rotation are of airfoil shape, the upstream facing sides of the blades being curved backwardly from the leading edge and the rear or trailing portions tapering to avery small or negligible thickness at the trailing edge. The maximum thickness of the blade is therefore closer to the leading edge, the forwardly facing side of the blades being substantially curved while the pushing side of the blades is slightly con- 'vexed or flat. This arrangement of the blade sections not only provides for very efllcient movement of the air as the ventilator rotates at some fixed point and produces a ventilating flow, but is also efiective in producing the minimum amount of air turbulence and thus aids in the reduction of noise, With the various described features in combination the entire blade is such as to move a very large volume of air in any given time but with far less noise than the usual ventilating fan constructions.

While the form of apparatus herein described constitutes preferred embodiment of the invention, it is to be understood that the invention is not limited to this precise form of apparatus, and that changes may be made therein without departing from the scope of the invention which is defined in the appended claims.

What is claimed is:

l. A rotatable air ventilating propeller adapted for operation with little noise, having a blade in whichthe leading edge from'a point about onehalf of the propeller radius from the axis of rotation' outto the blade tip is swept back at an angle of the order of 45 degrees to a radial line from the axis of rotation and in which the blade sections are of airfoil contour and of outwardly decreasing angles of attack with their chord length centers contained in a line which is swept back throughout at least the outer half of the blade length.

2. A rotatable air ventilating propeller adapted for operation with little noise, having a blade the leading edge of which from about one-half the propeller radius from the axis of rotation out to the blade tip is swept backat a large angle to a radial line from the axis of rotation. the chord length centers from about one-half the propeller radius out to the blade tip being contained in a line which is swept back at a substantial angle, said blade having sections taken at difierent distances from the axis of rotation helically displaced 5 relatively for outwardly decreasing angles of attack, with the chord length outwardly decreasing in a gradual manner substantially to the blade tip from a maximum length which is at a point about half the propeller radius from the blade tip, and 10 with the chord length centers of the sections from the mid portion of the tip of the blade forming a line extending at' a substantial angle to a radial line from the axis of rotation.

3. A rotatable air ventilating propeller-adapt- 15 ed for operation with little noise, having a blade in which the leading edge is swept back from the mid portion of the blade to the blade tip at a large angleto a radial line from the axis of rotation, said blade having a sectional contour 20 of airfoil shape with the sections taken at different distances from the axis of rotation helically displaced relatively for outwardly decreasing angles of attack and with the chord length centers of the sections from about the mid portion 25 to the tip forming a line which is swept back at a substantial angle, the blade length as measured from the axis of rotation being about three times the maximum chord length.

4. A rotatable air ventilating propeller adapt- 30 ed for operation with little noise,.having a blade in which the leading edge is swept back from about the mid portion of the blade to the blade tip at a large angle to a radial line from the axis of rotation, said blade having a sectional con- 35 tour of airfoil shape with the sections taken at diiferent distances from the axis of rotation disthe axis of rotation being about three times the maximum chord length and with the maximum cord length at about the mid portion of the 45 blade.

5. A rotatable air ventilating propeller adapted for operation at high speed with little noise, having a blade the leading edge of which from about the mid-length of the blade to the tip of the blade is swept back at an angle of the order of 45 degrees, said blade having asectional contour of airfoil shape with the sections taken at different distances from the axis of rotation being displaced relatively for outwardly decreasing angles of attack and with the chord length centers of the sections from about the mid portion of the blade to the tiptof the blade forming a line which is swept back at a substantial angle, the trailing edge of the blade departing materially from a radial plane through the rear of the tip and containing the axis of rotation, the blade length being about three times the maximum chord length and the maximum chord length being provided approximately midway of the length of the blade.

6. A rotatable air ventilating propeller having a plurality of bird-wing shaped blades of airfoil section in each of which the leading edge extends outwardly from the hub portion in a forward (11- rection and from about the mid portion of the blade to about the blade tip is swept back at an angle of the order of 45 degrees, the centers of the chord lengths from the mid portion of the blade to the blade tip being contained in a line which is also swept back at a substantial angle the length of the blade not exceeding three times the maximum chord length.

7. A rotatable air ventilating propeller adapted for operation with little noise at high speeds, having a blade the leading edge of which curves gradually from the hub portion and which is swept back for at least the outer half of the propeller radius at an-angle'of. the order of 45 degrees to a radial line from the axis of rotation, the chord length centers from about one-half of the propeller radius up to; the blade tip being swept back, said blade having a sectional contour of airfoil shape with the sections taken at different distances from the axis of rotation be- 7 ing helically displaced relatively from one another'for' outwardly decreasing angles of attack, and decreasing outwardly in chord length to the blade tip irom'a maximum length which is about half the propeller radius from the blade tip.

'8. A rotatable air ventilating propeller adapted for operation with little noise, having a blade the leading edge of which is swept back from a point about half way between the blade tip and the propeller axis and out to the blade tip at a large angle to a radial line from the axis of rotation, the chord length centers from about onehalf of the propeller radius upto the-blade tip 10 being swept back, said blade having a sectional contour of airfoil shape with the sections taken outwardly decreasing angles of attack, and de- 15 creasing outwardly in chord length to the blade tip from a maximum length which is about half g the propeller radius from the blade tip.

. I FREDERICK CHARAVAY. 

